Legitimate?
I think so.
Probably depends on one’s definition.
Stanton Friedman at
http://www.stantonfriedman.com
has the best analysis and discussion of the MJ-12 DOCS that I’ve read.
My own take is probably similar to his . . . there’s plenty of convincing elements to them.
They were probably released either by a whistle-blower or as a trial balloon or as part of some complex disinformation campaign.
There’s some flags on the play. But there’s also, to my mind, plenty of congruent corroborated stuff in them.
I think, IIRC, that Stanton kind of shreds some of the carping against their authenticity but still takes a kind of middle road position on their being authentic.